Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/48—Separation; Purification; Stabilisation; Use of additives
  • C07C67/52—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation
  • C07C67/54—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation by distillation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
  • B01D3/14—Fractional distillation or use of a fractionation or rectification column
  • B01D3/143—Fractional distillation or use of a fractionation or rectification column by two or more of a fractionation, separation or rectification step
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
  • C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
  • C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
  • C07C29/80—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by distillation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/39—Preparation of carboxylic acid esters by oxidation of groups which are precursors for the acid moiety of the ester
  • C07C67/40—Preparation of carboxylic acid esters by oxidation of groups which are precursors for the acid moiety of the ester by oxidation of primary alcohols
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
  • B01D2257/702—Hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C31/00—Saturated compounds having hydroxy or O-metal groups bound to acyclic carbon atoms
  • C07C31/02—Monohydroxylic acyclic alcohols
  • C07C31/04—Methanol
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
  • C07C69/52—Esters of acyclic unsaturated carboxylic acids having the esterified carboxyl group bound to an acyclic carbon atom
  • C07C69/533—Monocarboxylic acid esters having only one carbon-to-carbon double bond
  • C07C69/54—Acrylic acid esters; Methacrylic acid esters
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/10—Process efficiency

Definitions

• the invention relates to an integrated process for purification of a methyl methacrylate (MMA) reaction product from the effluent of an oxidative esterification reactor (OER).
• MMA methyl methacrylate
• OER oxidative esterification reactor
• the present invention is directed to a process for purifying methyl methacrylate; said method comprising: (a) feeding a reaction product mixture comprising methanol, methyl methacrylate and alkali metal salts thereof, methacrolein, water and heavy byproducts to a first distillation column having at least 15 trays; wherein said reaction product mixture and a C 6 -C7 hydrocarbon enter the first distillation column above the middle of the distillation column; (b) removing a first overhead stream comprising C 6 -C7 hydrocarbon, methacrolein, methanol, water and methyl methacrylate; (c) removing a first bottoms stream comprising water, methyl methacrylate and alkali metal salts thereof and heavy byproducts; (d) feeding the first overhead stream to a first water separator to produce (i) a first organic phase which is returned to the first distillation column and (ii) a first aqueous phase which enters a methanol drying distillation column which produces a second overhead
• the Figure is a schematic of a process of the invention.
• alkali metal salts are sodium or potassium salts, preferably sodium.
• the C 6 -C7 hydrocarbon functions as an entrainer. It is believed that it breaks the methanol/MMA azeotrope, allowing removal and recovery of methanol in the first distillation column.
• the C 6 -C7 hydrocarbon is aliphatic.
• the C 6 -C7 hydrocarbon is a saturated hydrocarbon, preferably an acyclic alkane. In one preferred embodiment, a mixture of C 6 -C7 hydrocarbons is used.
• the C 6 -C7 hydrocarbon or mixture thereof has an atmospheric pressure (101 kPa) boiling point from 65 to 100°C, preferably at least 67°C; preferably no greater than 90°C, preferably no greater than 80°C, preferably no greater than 75 °C.
• the C 6 -C7 hydrocarbon is n-hexane.
• the first distillation column (methanol recovery column) has at least 20 trays, preferably at least 25; preferably no more than 40 trays, preferably no more than 35 trays.
• the point at which the reaction product mixture enters the first distillation column is in the highest 40% of the trays, preferably the highest 30%, preferably the highest 20%, preferably the highest 10%, preferably the highest 7%.
• the point at which the reaction product mixture enters the first distillation column is in the highest ten trays, preferably in the highest eight trays, preferably in the highest six trays, preferably in the highest four trays, preferably in the highest three trays, preferably in the highest two trays, preferably in the top stage.
• the methanol drying distillation column has from 20 to 40 trays;
• the MMA stripper distillation column has from 5 to 30 trays;
• the MMA drying distillation column has from 20 to 40 trays;
• the MMA product distillation column has from 10 to 30 trays;
• the reaction product mixture comprises at least 0.8 wt% methyl methacrylate alkali metal salts, preferably at least 1 wt%, preferably at least 1.5 wt%, preferably at least 1.8 wt%; preferably no more than 3 wt%, preferably no more than 2.5 wt%, preferably no more than 2 wt%.
• the reaction product mixture comprises from 40 to 80 wt% methanol, preferably from 45 to 70 wt%, preferably from 50 to 68 wt%.
• the reaction product mixture comprises from 5 to 40 wt% methyl methacrylate, preferably from 10 to 35 wt%, preferably from 15 to 32 wt%.
• the reaction product mixture comprises from 1 to 10 wt% water, preferably from 3 to 9 wt%, preferably from 4 to 8 wt%.
• the amount of the C 6 -C7 hydrocarbon(s) which enters the first distillation column as reflux is from 2 to 10 times the amount of methanol in the product mixture, preferably 3 to 5 times.
• additional C 6 -C7 hydrocarbon when additional C 6 -C7 hydrocarbon needs to be added, it enters the first distillation column in the highest ten trays, preferably in the highest eight trays, preferably in the highest six trays, preferably in the highest four trays, preferably in the highest three trays, preferably in the highest two trays, preferably in the top tray.
• the direct product from the OER passes through an initial distillation column to remove an initial overhead stream comprising light components, i.e., those having higher vapor pressure than methanol.
• the light components principally comprise methyl formate.
• Typical levels of methyl formate in the direct product are from 1 to 6 wt% and the initial bottoms stream from the initial distillation column is fed to the first distillation column as the reaction product mixture, which typically contains no more than 1 wt% methyl formate.
• the first overhead stream passes through a condenser and then enters a first water separator, from which the first organic phase is returned to the same section of the first distillation column where the product mixture enters, and the first aqueous phase is sent to a methanol drying column.
• the first aqueous phase comprises 50-68% water, 30- 44% methanol and 2-6% methacrolein.
• the first organic phase comprises 82- 92% C 6 -C 7 hydrocarbon, 4-10% methacrolein and 2-10% MMA.
• At least a portion of the second bottoms stream, which is rich in water, is added to the first overhead stream before it enters the first water separator.
• the amount of water added to the first overhead stream is 0.2 to 1 times the amount of the overhead stream, preferably 0.25 to 0.6 times.
• the first bottoms stream enters a second water separator after passing through a heat exchanger to cool it, preferably to a temperature no greater than 50°C, preferably from 20 to 50°C.
• the second organic phase is predominantly MMA (preferably 86-96%), with the remainder comprising mostly water (1-4%) and heavy byproducts (3-10%), and is processed further to obtain high-purity MMA.
• the second organic phase is combined with at least a portion of the second bottoms stream and sent to the third water separator, from which a third organic phase is sent to an MMA drying distillation column and a third aqueous phase is produced.
• the third aqueous phase is combined with the second aqueous phase being sent to the MMA stripper column.
• the first aqueous phase is fed to a methanol drying column to remove water.
• the second overhead stream from this column comprises 82-92% methanol, 7- 14% methacrolein and 0-4% MMA.
• the second overhead stream is recycled to the OER.
• the second aqueous phase contains methyl methacrylate alkali metal salt and water, preferably 70-90% water and 10-30% sodium MMA, as well as small amounts (0-2%) of MMA and methanol.
• the second aqueous phase enters an MMA stripper column which produces a third overhead stream rich in water and preferably comprising MMA (5-15%) and a small amount of methanol (2-6%).
• the third overhead stream is sent to the first distillation column along with the product mixture.
• the MMA drying column removes water from the crude MMA.
• the fourth overhead stream from this column comprises 75-85% MMA, 15-22% water and 0- 3% methanol.
• the fourth overhead stream is sent to the first distillation column, preferably to the middle third of the column, preferably below the point at which the reaction product mixture enters the column.
• the fourth bottoms stream from this column comprises 90-96% MMA and 4-10% heavy byproducts.
• the fourth bottoms stream is fed to an MMA product distillation column which removes the heavy byproducts to produce an MMA overhead stream which preferably is 99-100% purity and a fifth bottoms stream which comprises MMA and heavy byproducts.
• Water may be decanted from a stream by the means of standard methods.
• a vessel that contains a vertical baffle or a series of baffles and is sized sufficiently that the organic and aqueous phase separate into individual phases.
• the lighter phase organic proceeds over the vertical baffle and the heavier water phase flows underneath the baffle.
• the separated liquids are withdrawn from the sections of the vessel that have accumulated the overflow and underflow of each phase.
• polymerization inhibitor is added to one or more of the columns to minimize polymerization of MMA.
• Amounts of inhibitor typically are small and types and typical use amounts are well known in the field.
• the temperature and pressure in a distillation column is dependent on the composition of the material being distilled.
• the columns are operated at reduced pressure, such as from about 100 to about 760 mmHg (13 to 101 kPa), or from 200 to 400 mmHg (26 to 53 kPa).
• the column pressure is adjusted to keep the bottoms temperature below 120°C, preferably below 100°C.
• reaction product mixture 1 is introduced into first distillation column A.
• a first bottom stream 6 from the column is split, with stream 8 passing through a heat exchanger E, and recycle 7 returned to the column through reboiler D.
• Overhead stream 2 leaves the column at the top and passes through condenser B and the resulting stream 3 enters water separator C, to produce (i) a first organic phase 4 which is returned to the first distillation column and (ii) a first aqueous phase 5 which enters methanol drying distillation column G which produces a second overhead stream 9 rich in methanol and a second bottoms stream 10 which is rich in water, and at least a portion of the second bottoms stream is fed to the first water separator.
• Stream 8 is fed to a second water separator F to produce (i) a second aqueous phase 13 which is fed to an MMA stripper distillation column I which produces a third overhead stream 14 rich in water and a third bottoms stream 15 comprising water and methyl methacrylate sodium salt, and (ii) a second organic phase 16.
• Second organic phase 16 and a portion of second bottoms stream 10 are fed into a third water separator H which produces (i) a third organic phase 12 which enters an MMA drying distillation column J which produces a fourth overhead stream 17 and a fourth bottoms stream 18, and (ii) a third aqueous phase 11.
• Fourth bottoms stream 18 is fed to an MMA product distillation column K which produces an MMA product stream 19 and a bottoms stream 20.
• the distillation column is a 28 mm i.d. 30-tray Oldershaw column, and n-hexane is employed as the entrainer solvent.
• a steam-heated thermosiphon reboiler is used to provide the boil-up in the column.
• the pressure at the top of the column is 700 mmHg absolute.
• the overhead temperature is 48°C, and the bottoms temperature is 83 °C.
• the efficiency of the first column increases as the location of the reaction product mixture feed rises in the column.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Crystallography & Structural Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Treatment Of Liquids With Adsorbents In General (AREA)

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